1. Field of the Invention:
This invention relates to a cold water curable orthopedic cast forming material in the form of a bandage.
Orthopedic structures find wide use in the immobilization of limbs in aid of the healing process. In the maintenance of fixation of fractured bones, immobilization of inflamed or injured joints, in cases of disease or trauma, and for the support and immobilization of ligamentous and muscular structures in instances of strains and sprains, it is necessary to encase the limb in a partially or completely surrounding rigid form or cast. The immobilized limb may be encased in such rigid structure for long periods of time, frequently as much as 6 weeks or more.
There are two major considerations for a cast. The first consideration concerns the formation of the cast. A satisfactory cast material should be easily handleable, should not have properties which deleteriously affect the limb, particularly, the skin, should have a reasonable setting time or work life, so as to allow a reasonable period of time in which to mold the cast material about the limb, should be flexible during application to the limb so as to readily assume the shape of the limb, should be free of offensive or noxious solvents or other such chemicals, and should set within a relatively short time under relatively mild conditions. In addition, it is desirable that a minimum of equipment should be involved in formation of the cast. Also, it is desirable that during the forming of the cast the material does not generate an uncomfortable exothermic reaction, and that upon drying, curing or setting up it has a negligible shrinkage factor.
The second consideration concerns the properties of the cast after it is formed. Desirably, the cast should be of a light weight material so as to minimize the inconvenience to the wearer, porous so as to allow the underlying skin to breathe and not become macerated or otherwise irritated, should have sufficient structural strength so as to retain its structure under normal usage, should be sufficiently sturdy to maintain the joint or limb in the immobilized position and protect the joint or limb from jars, and should be easily removable. An optimum cast should also be water-proof, i.e. the coated fabric material itself should not absorb and retain water, be as X-ray transparent as possible, and be highly impact and abrasion resistant.
In this regard, U.S. Pat. No. 2,711,168 discloses a cast-forming element comprising a base warp knit fabric and plaster of Paris coated thereon; U.S. Pat. No. 3,048,169 discloses the formation of casts by reacting ingredients in an impermeable envelope to form a thermoplastic resin and then shaping the resin about the limb; U.S. Pat. No. 3,301,252 discloses the formation of casts by spraying a foamable composition over the affected area of the limb and allowing a solidified foam to form; U.S. Pat. No. 3,630,194 discloses cast formation using a bandage material supporting a solid, water-soluble vinyl monomer, dipping the same into water in the presence of a catalyst for polymerization, wrapping the limb with the bandage and allowing polymerization to take place; U.S. Pat. No. 3,631,854 discloses cast formation using an inflatable, double-walled sleeve which is placed about the affected limb, filled with a liquid, curable composition, and then allowed to harden; U.S. Pat. No. 3,787,272 discloses an air-permeable, glass fiber fabric for use in orthopedic casts; U.S. Pat. No. 3,882,857 discloses an orthopedic cast comprising an inner protective sleeve and an outer immobilizing structure; U.S. Pat. No. 4,105,025 discloses a method of cast formation wherein a bandage impregnated with a crystallizable polyurethane is heated above the melting point of the polyurethane, wrapping the affected body member with the bandage and then allowing the same to cool and thereby crystallize or harden; U.S. Pat. No. 4,131,114 discloses cast formation using a package containing a carrier material and in separate compartments the reactive components necessary to form a curable resin, wherein for application the reactive components must be brought together, impregnated into the bandage, excess removed and then the bandage must be applied to the affected limb and allowed to cure; U.S. Pat. No. 4,215,684 discloses a net bandage comprising elastic and non-elastic fibers; and German Offenlegungschrift No. 2,651,089 discloses a bandaging material comprising a fabric impregnated and/or coated with a prepolymer which is the reaction product of at least one aromatic polyisocyanate and at least one polyol containing tertiary amino nitrogen.
Because of the numerous and varied requirements for an orthopedic cast material, none of the presently known immediately available cast materials provide all or substantially all of the properties indicated above.
A need therefore continues to exist for a cast material which is strong and thin, drapable, not abrasive, easy to cut, having a low exotherm, exhibits good breathabilty, is X-ray transparent and has a good package shelf life.